Final answer:
In object-oriented programming, when a method in a subclass provides a unique implementation to an existing method from its superclass, it is said to be overridden.
Step-by-step explanation:
A method that has been overridden in at least one subclass is said to be overridden. When a method is overridden, the subclass provides its own specific implementation of a method that already exists in its superclass. Overriding is a feature in object-oriented programming that lets a subclass or child class provide a unique implementation of a function that is also available in one of its parent or superclass classes.